A California sea turtle advocacy group and a Florida fishing association filed a federal lawsuit in San Francisco Thursday accusing the U.S. State Department of allowing foreign fishermen to sell shrimp in the United States caught by nets that kill sea turtles.

The lawsuit filed by the Turtle Island Restoration Network in Forest Knolls and the Mayport Village Association claims regulators hardly ever monitor overseas shrimp fleets but nevertheless allow them to sell shrimp in violation of the Endangered Species Act.

"They are required to certify countries that sell shrimp in the United States every year. The truth is most times they don't even visit the country," said Todd Steiner, a Marin County-based biologist who is executive director of the Turtle Island Restoration Network. "Shrimping kills more sea turtles than all other fishing technologies combined. They drag nets for six or seven hours at a time and the sea turtles drown in the nets. They can't come up for air."

Steiner said U.S. fishermen are required to use a grate-like contraption called a Turtle Excluder Device, or TAD, that allows turtles to pass through nets, but foreign fishermen regularly ignore that rule, killing tens of thousands of turtles.

"Our Mayport shrimpers are struggling to survive, while foreign fleets get a free pass on the law and flood the market with cheap shrimp," said Al Millar, representing the Mayport Village Civic Association and its small fleet of family shrimpers based in the historic village of Mayport, Fla.

The lawsuit, filed in U.S. District Court in San Francisco, accuses the State Department of failing to enforce the use of TADs by foreign shrimp vessels and demands additional environmental oversight and review of the foreign shrimp certification process. The shrimp fishery, the country's top seafood import, was worth $3.9 billion last year.

A State Department spokesman said the office was not prepared to comment.

Imports of shrimp from Costa Rica were recently banned after environmentalists connected to the nonprofit Turtle Island network presented evidence that boats were not using excluder devices. But, Steiner said, there are 15 other nations that were certified with little, if any, scrutiny.

"We can't go around the world to different countries and provide that data," he said. "They're supposed to do it."

Americans are gluttonous when it comes to shrimp, downing more than 500,000 tons a year, about 90 percent of which is imported.